The present invention relates to a device for rotary conversion of a web or sheet matter in a machine mainly manufacturing paper, cardboard or plastic folding box blanks in the packaging industry in particular.
The conversion of a cardboard web into folding box blanks, for example, consists of printing it, of embossing the parts intended to appear in relief, of creasing it where desired and of cutting it while simultaneously stripping undesirable waste resulting from cutting. All these operations are carried out in successive processing stations driven in synchronism which constitute the packaging manufacturing machine.
The invention is mainly of use in the said embossing, creasing and cutting operations. Each operation uses corresponding rotary tools which act successively on the web.
A station for cutting a web by rotary tools, which generally consist of an upper cutting tool and a lower smooth cylindrical anvil, will be taken as an example to describe the arrangement of such stations. The upper tool and the lower anvil, between which the web matter is cut, are mounted in bearing blocks arranged in a cassette disposed between the side frames of the machine processing the web. The bearing blocks are inserted by sliding them in the vertical direction between the inner edges of the cassette which forms the bearing structure of these blocks. The lower and upper rotary tools are driven at the same angular speed but in opposite direction to one another by gears having diameters chosen so as to leave only a short distance between the upper tool and the lower anvil. In order to ensure the interval separating these two tools very precisely (about 1 μm), each end of the upper tool and the lower anvil comprises a bearing crown and a fine control system including adjusting wedges equipped each with a micrometric threading. The bearing blocks of the upper tool are connected with those of the lower anvil by a flexible coupling device and pressed against one another by rods or cylinders allowing to apply the desired cutting pressure while respecting the radial interval between the two rotary tools. Such a device is described more in detail in patent CH691116.
Each machine manufacturer generally has its own system of cassette inserted in each of the embossing, creasing, cutting or even printing stations as described in patent EP0113601. Some manufacturers have the cutting cassette resting on the bottom of the housing where it will be inserted, whereas others have it suspended in its median part of pins which enable it to be fixed at a constant reference level corresponding to the passage plane of the web or the sheets, whatever the diameter of the rotary tools defining the cutting format may be.
Some manufacturers have chosen a system of cassette forming a rigid unit in which the upper cutting tool and the lower anvil have been adjusted as much as possible outside the machine, whereas other manufacturers have less powerful systems, but quite as reliable, requiring adjustments in machine of the position of these two tools, not only to one another but also one and the other with respect to the machine frame. Effectively, in any case the meticulous adjustments of the spacing of the tools, their parallelism and their relative orientation in the horizontal and vertical planes should be carried out to allow a perfect cutting and a minimal wear of the cutting rules. As shown in document FR2556268, it is also known to tighten the tools in their housing, by exerting a constraint on the tools piled up in the cassette between its upper part and the bottom of the housing of the machine frame.
According to various possible embodiments, these stations are driven either all from the same machine side, or alternately from one side then the other. In this last case, the power sources for driving the cylindrical tools of the cassettes are not all on the same machine side. The prior art also shows that the drive systems completely differ according to the system of cassette provided by each manufacturer. Some use an adjustable arm, commonly called swivel arm, allowing to adapt the position of the driving toothed wheel to that of the output pinion of the cassette, the dimension of which each time varies according to the diameter of the cutting tool imposed by the cutting format required by the customer. Other manufacturers solved the engagement problem in another way, either by a specific arrangement of the whole cassette with respect to the machine frame, as shown by the kinematic chain illustrated in patent U.S. Pat. No. 4,674,377, or by a system of independent drive exclusively for the rotary cutting unit as shown in patent FR2695588. This prior art has the motor located on one of the side walls of the cutting unit, at a fixed given height, ensuring the direct drive of one cylindrical tool, whereas the other cylindrical tool must be moved in machine by a system of levers, cylinder and eccentric bearings, in the direction of the first tool so as to be also driven by the toothed wheel of the latter.
The great variety of the drive means and systems of arrangements of cassettes in the converting station renders a tool exchange between machines from different manufacturers completely impossible. Considering the very high manufacturing cost (about Euro 100'000) of a pair of cylindrical tools specifically adapted to convert only one type of packaging box of a certain format, it is thus unreasonable that a tool exchange between machines is not possible. This is particularly disadvantageous for a company or an independent who will change the trademark of machines. The same problem arises for a company willing to increase or partly renew the machine stock by more powerful production lines from another manufacturer. Obviously, with a plurality of machines from different manufacturers, it would be advantageous to be able to use one type of cassette on machines from different manufacturers. However, until now, the converting machines for producing packagings do not allow using a foreign important member, such as a cassette for rotary cutting from a competitive machine.